Dubai: Novak Djokovic returned to the tour after his historic triumph in Melbourne by beginning a bid for his 50th title with a surprisingly testing 6-4, 6-4 win over Canadian Vacek Pospisil.

The world number one was twice within a point of going 2-4 down in the second set against an opponent, ranked world 63, who hit freely, motivated by the chance of troubling someone who last month became the first man of the open era to win the Australian Open five times.

Djokovic also hopes to win his fifth title at the Dubai Open, which would put him just one behind Roger Federer`s record, and may ultimately benefit from the difficulties which Pospisil boldly imposed on him.

It was not till the ninth game that Djokovic could break serve, and only then with the help of Pospisil double fault, and when Djokovic broke early in the second set, Pospisil broke back immediately.

He did that with a dashing combination of attacks with had even the champion applauding.

But Djokovic knew how to win. "I just stayed mentally tough and stayed in the rallies. Once I got into the rallies I had better chance.

"He`s a very flashy player and serves well, and when there was a 15 percent drop in his first serve I knew I had a better chance. I think that decided the match."

Djokovic has more than half an eye on the French Open, the only Grand Slam title he has never won, even at this stage, three months before it begins.

He was therefore prepared, a little surprisingly, to comment on the fitness worries of Rafael Nadal, the nine-time French Open winner.

"He had a couple of big injuries that kept him away from the tour for six months?plus," said Djokovic, when told of Nadal claims that he is not in great shape.

"If he`s going to play as well as he did in previous years now in the clay court season or hard court, we don`t know. We don`t know what tomorrow brings. Obviously he didn`t play at the level, you know, that is recognizable for him in Australia."

Djokovic also knows that Nadal has recovered from injury problems before, and that he needs to focus on his own game.

Another distraction is thinking about the 50th title of his career. But when he was told that this would take him past the 49 career titles achieved by his coach Boris Becker, the temptation was briefly too much.

"I received that information and that`s why I have motivation more this week," Djokovic responded amidst laughter.

The man whom Djokovic beat in the Melbourne final, Andy Murray, also came through. Murray celebrateded his rise above Rafael Nadal into third place in the world rankings with a chequered straight sets win over Gilles Muller.

The Scot`s 6-4, 7-5 win over the Luxemburger illustrated how far the former Wimbledon and US Open champion has come in the one year since returning to the tour after a serious back operation.

It also showed that Murray`s return of serve and his trademark containing groundstrokes - almost always the bedrock of his game - were in good order, and suggested he has a solid basis from which to build his form over the week.

"Mentally I feel completely different, both in my body and in my mind, though there are still things I can do better," he said.

"Last year even if I was playing well I was doubting a lot of things - confidence in my body and in my game. Even if I was playing well I didn`t feel like I was. I feel much better at this stage than I did last year."

He now plays Joao Sousa, the world number 50 from Portugal, with a seed-free route to the semi-final after Marcos Baghdatis, the former Australian Open finalist from Cyprus, overcame David Goffin, the number eight from Belgium, 6-2, 7-5.

Djokovic plays Andrey Golubev, a former top 40 player from Kazakhstan.